It is well known that the probability of surviving a heart attack often depends critically on the speed with which appropriate medical care is provided. One of the most common and life threatening consequences of a heart attack is the development of a cardiac arrhythmia such as ventricular fibrillation in which the heart is unable to pump a significant volume of blood. When such an arrhythmia occurs, serious brain damage and death may result unless a normal heart rhythm can be restored within a few minutes. The most effective treatment for ventricular fibrillation is the application of a strong electric shock to the patient. Such an electric shock frequently terminates the chaotic activity characteristic of arrhythmia's, and restores the normal pumping action of the heart. Defibrillators for producing and delivering such shocks have been known and successfully used for many years. However, the size and cost of prior defibrillators, coupled with the risk they pose if used improperly, have restricted the use of defibrillators to hospitals and to emergency medical facilities. Many lives would be saved each year if defibrillators could be made more immediately available to heart attack victims.
The advances made in electronics have enabled the production of small, lightweight, and automatic defibrillators, which are portable enough to be hand carried along with a patient while the patient is being transported on a gurney. Defibrillators have also become available in many public gathering places. With such a proliferation of these life-saving devices, there is a need for a defibrillator which may be used by inexperienced as well as highly qualified individuals. Automated external defibrillators (AEDs), as they are called, are designed with an infrequent practitioner in mind. AEDs typically have a simplified routine which attempts to make even a nonpractitioner confident with using the defibrillator with only a modicum of basic training. Most AEDs generally operate in a “semi-automatic mode.” For example, the LIFEPAK® 500 AED manufactured by Medtronic Physio-Control Corp. and the FORERUNNER™ AED manufactured by Agilent Technologies have at least two command buttons: (1) an “on” button, and (2) a shock button which delivers a defibrillation pulse to the patient. In addition, the LIFEPAK® 500 AED includes a third button that prompts the AED to analyze the patient to determine whether shock treatment is indicated by monitoring the patient's heart rhythms or electrocardiogram (ECG). Manual delivery of “shock” treatment by pressing a button imparts to the user the seriousness of the event. However, the “shock” button can be eliminated so that the AED delivers the defibrillation pulse to the patient automatically and without human intervention upon detection of a shockable rhythm. Such AEDs are typically referred to as operating in an “automatic” mode. For purposes of the following description, the term “AED mode” may apply to either an automatic or semi-automatic mode.
While the operation of AED controls may appear intuitive, it is to be remembered that AEDs are used in highly stressful situations, where little time for deliberate thought is available. In short, a rescuer must act fast and has little time to decipher the controls on a complicated piece of equipment in which he may have only received basic training. Consequently, the user interface for such AEDs must be as simple and uncluttered as possible. However, AED manufacturers are also striving to provide more sophisticated controls for those highly trained individuals who arrive at the care giving location at a later time. These more experienced personnel are fully comfortable with a defibrillator and an array of many user input commands to more specifically tailor the shock treatment to the patient. Therefore, attempts are being made to combine a simplified or “AED mode” for infrequent rescuers and a “manual mode” for skilled rescuers in one defibrillator apparatus. The goal is to provide a visually uncluttered appearance and somehow differentiate between modes for an infrequent rescuer so as not to befuddle the rescuer, while at the same time providing a host of manual user input commands for the highly trained individual.
Several approaches have been attempted with varying degrees of distinction between manual and AED modes. For example, the LIFEPAK® 300 AED manufactured by Medtronic Physio-Control Corp. can be operated in a semi-automatic mode or a manual mode. To enter the manual mode, the rescuer simply had to press a manual access button located on the front panel of the AED. The remaining buttons on the front panel are soft keys that remain accessible and change function according to the mode of the defibrillator and the corresponding message on the defibrillator's display. Other manufacturers have attempted to use brightly colored or marked command buttons or dials to distinguish between different modes. Unfortunately, in both these approaches, the rescuer is forced to interpret and differentiate between buttons, softkeys and/or displays or otherwise read and process information, in order to operate the device which only increases the possibility of human error.
In U.S. Pat. No. 6,021,349 to Arand et al., an attempt is made to deal with the problem by hiding a “change to manual personality” button behind an access door to prevent accidental depression of the manual button and send the defibrillator into a manual “personality” without the rescuer becoming aware. However, as with the LIFEPAK® 300 AED, the remaining buttons on the front panel of the defibrillator remain accessible and change function according to the mode of the defibrillator and the corresponding message on the defibrillator's display. Consequently, this approach does not solve the problem of providing an uncluttered user interface to prevent the rescuer from having to interpret and distinguish manual command buttons from AED command buttons.
Accordingly, there is a need for a defibrillator having manual, semi-automatic and/or automatic modes which provides a clean and intuitive user interface for selecting, operating, and switching between such modes. However, unintentional shift of the defibrillator from one mode to another should be prevented.